A cellular communications network typically includes a variety of communication nodes coupled by wireless or wired connections and accessed through different types of communications channels. Each of the communication nodes includes a protocol stack that processes data transmitted and received over the communications channels. Depending on the type of communications system, the operation and configuration of the various communication nodes can differ and are often referred to by different names. Such communications systems include, for example, a Code Division Multiple Access 2000 (CDMA2000) system and a Universal Mobile Telecommunications System (UMTS).
Third generation wireless communication protocol standards (e.g., 3GPP-UMTS, 3GPP2-CDMA2000, etc.) employ a dedicated traffic channel in the uplink (e.g., a communication flow between a mobile station (MS) or User Equipment (UE), hereinafter referred to as a user, and a base station (BS) or Node B. The dedicated physical channel may include a data part (e.g., a dedicated physical data channel (DPDCH) in accordance with UMTS Release 4/5 and 6 protocols) and a control part (e.g., a dedicated physical control channel (DPCCH) in accordance with UMTS Release 4/5 and 6 protocols).
FIG. 1 illustrates a conventional wireless communication system 100 operating in accordance with UMTS protocols. Referring to FIG. 1, the wireless communication system 100 may include a number of Node Bs such as Node Bs 120, 122 and 124, each serving the communication needs of users 110 in their respective coverage area. The Node Bs are connected to an RNC such as RNCs 130 and 132, and the RNCs are connected to a MSC/SGSN 140. The RNC handles certain call and data handling functions, such as, autonomously managing handovers without involving MSCs and SGSNs. The MSC/SGSN 140 handles routing calls and/or data to other elements (e.g., RNCs 130/132 and Node Bs 120/122/124) in the network or to an external network. Further illustrated in FIG. 1 are interfaces Uu, Iub, Iur and Iub between these elements.
FIG. 2 illustrates an example of a frame structure for a UMTS uplink dedicated physical channel. As shown, each frame 200 may have a length of, for example, 10 milliseconds (ms) and may be partitioned into 15 slots 205. Each slot 205 may have a length of 2560 chips, which corresponds to one power-control period, and may have a duration of 2/3 ms.
The uplink dedicated physical channel includes a DPDCH 240 and a DPCCH 220. The DPCCH 220 and the DPDCH 240 may be code multiplexed. The uplink DPDCH 240 carries information (e.g., voice, data, video, etc.) transmitted from users 110 to NodeBs 120/122/124.
The DPCCH 220 includes 15 slots per radio frame, where 1 radio frame is 10 ms in duration. The DPCCH carries control information, such as, a pilot signal 221, transmit power control information (e.g., transmit power control (TPC) bits) 222, a transport format combination indicator (TFCI) value 223 and feedback information (FBI) 224 (which may or may not be used). The TFCI 223 informs the Node B 120/122/124 of the transport format information (e.g., voice and/or data packets sizes, coding types, etc.) transmitted by users 110. For example, TFCIs indicate the composition of a transport channel (TrCh) among a plurality of transport channels carried by the corresponding DPDCH.
FIG. 3 illustrates a conventional uplink transmitter and receiver.
Referring to FIG. 3, well-known DPCCH frames used in determining channel estimates are modulated at a BPSK Modulator 205, and the modulated frames are orthogonally spread at an orthogonal spreading unit 210. The output from the orthogonal spreading unit 210 is gain adjusted at gain unit 215 and output to combiner 220.
At transport channel processing block 202, data associated with upper layer transport channels (TrChs) is processed into DPDCH frames. That is, for example, the transport channels are mapped onto the DPDCH. A conventional manner in which this is performed will be discussed in more detail with regard to FIG. 4.
FIG. 4 is flow diagram of a well-known conventional uplink Transport Channel Multiplexing and Coding process in 3GPP UMTS described, for example, in 3GPP TS 25.212 version 5.10.0 Release 5 (Universal Mobile Telecommunications System (UMTS); Multiplexing and channel coding (FDD)). Because such a flow diagram is well-known in the art, only certain portions will be discussed for the sake of brevity. The flow diagram in FIG. 4 illustrates processes performed at the transport channel processing block 202 of FIG. 3.
Referring to FIGS. 3 and 4, at the transport channel processing block 202, each upper layer transport channel undergoes a number of processes including coding, interleaving, etc., and several transport channels are multiplexed into form a “Coded Composite Transport Channel (CCTrCH).” Control information is added and the overall signal is mapped onto the DPDCH.
As is well-known, each transport channel is associated with a Transfer Format (TF), which depends on the type of data (e.g., video, speech, Internet, etc.) and the associated transfer rate. Each set of multiplexed transport channels or CCTrCh corresponds to a specific combination of transport formats known as a Transport Format Combination (TFC). Information regarding the TFC for a set of multiplexed transport channels and how the transport channels are assembled into the DPDCH is sent from transmitter to receiver in the above-discussed TFCI.
Referring back to FIG. 3, the DPDCH frames generated by the transport channel processing block 202 are binary phase shift keying (BPSK) modulated at BPSK modulator unit 216, and orthogonally spread at the orthogonal spreading unit 222. The spread modulated frames are gain adjusted by gain unit 240. The gain adjusted frames are output to the combiner 220.
The outputs of each of the gain units 215 and 240 are combined at combiner 220, and the resultant signal is output to scrambling and shaping filter 225. The resultant signal is scrambled and filtered by scrambling and shaping filter 225. The filtered signal is sent to the receiver 500 via propagation channel 330 (e.g., over the air).
At the receiver 500, the transmitted signal is received over the propagation channel 330, and input to DPDCH physical channel processing block 555 and DPCCH processing block 504.
Within the DPDCH processing block 555, DPDCH soft-symbol generation block 502 processes the received signal over a radio frame within the current transmission time interval (TTI) TTI_N to recover a DPDCH soft-symbol sequence. The well-known TTI is a wireless network parameter referring to the length of an independently decodable transmission on the radio link. The TTI is related to the size of data blocks passed from the higher network layers to the radio link layer. Each DPDCH soft-symbol sequence represents an estimate of a corresponding DPDCH frame output from the transport channel processing block 202 in the transmitter 200. In one example, the DPDCH soft-symbol generation block 502 processes the received signal over the current radio frame N to partially recover DPDCH soft-symbols up to a given spreading factor interval (e.g., a minimum allowed spreading factor interval), hereinafter referred to as data frame DN. Operations performed at the DPDCH soft-symbol generation block 502 include matched-filtering, descrambling, a first DPDCH despreading and a first DPDCH demodulation operation, each of which are well-known in the art, and thus, will only be described briefly herein for the sake of brevity. At the DPDCH soft-symbol generation block 502, the first de-spreading and demodulation operations do not require TFCI information to generate data frames.
The DPDCH soft-symbol generation block 502 outputs the recovered data frame DN to a frame buffer 506. The frame buffer 506 buffers the data frame DN for a length of time equal to the length of the current radio frame N and outputs the buffered data frame DN to the despreading and TrCh demultiplexing block 508.
While generating and buffering the data frame DN, the DPCCH processing block 504 processes the received signal to generate a sequence of control information soft-symbols (e.g., TFCI soft symbols, herein referred to as a control frame CN) corresponding to the data frame DN. The control frame CN is decoded to recover control information TFCI_N received over the current radio frame N. The control information TFCI_N may include, for example, transfer format information or a TFCI word for corresponding data frame DN. Operations performed at the DPCCH processing block 504 include matched-filtering, descrambling, a DPCCH despreading and a DPCCH demodulation operation, each of which are well-known in the art, and thus, will not be described any further herein for the sake of brevity.
The recovered TFCI word TFCI_N may be output to the despreading and TrCh demultiplexing block 508.
Still referring to FIG. 3, the despreading and Trch demultiplexing block 508 despreads the data frame DN, and demultiplexes the set of transport channels TrCh0, TrCh1, . . . TrChn within the data frame DN using the TFCI word TFCI_N from the DPCCH processing block 504 to generate a transport channel frame TrChF0-TrChFn associated with each of the transport channels TrCh0-TrChn. Because the despreading and transport channel demultiplexing performed at the despreading and TrCh demultiplexing block 508 is well-known in the art, a further discussion will be omitted for the sake of brevity.
The plurality of transport channel frames TrChF0-TrChFn may be output to a corresponding one of a plurality of rate de-matching blocks 510_0, 510_1, . . . , 510_n. Through well-known rate de-matching, each of the plurality of rate de-matching blocks 510_0-510_n recovers bits (or transport channel data) transmitted in a corresponding one of transport channel frames TrCHF0-TrChFn using the TFCI word TFCI_N from the DPCCH processing block 504. Each of the plurality of rate de-matching blocks 510_0-510_n outputs transport channel data for a corresponding one of the transport channel frames TrChF0-TrChFn to a corresponding one of a plurality of transport channel processing blocks 512_0, 512_1, . . . 512_n. Each of the plurality of transport channel processing blocks 512_0-512_n processes the received transport channel data to recover the transmitted data or data stream. As is well-known, transport channel processing includes, for example, decoding, CRC check, etc.
Conventionally, a TFCI word is transmitted each radio frame, but remains unchanged over the ° FI for all transport channels multiplexed on the DPDCH. Conventional TFCI processing at the DPCCH processing block 504 attempts to recover TFCIs each radio frame, and use the recovered TFCI word to process the DPDCH. However, conventional TFCI processing does not check whether TFCI words in consecutive radio frames (e.g., N, N+1, . . . N+m) within a TTI are the same or identical, before recovering the TFCI word in each radio frame. Because the TFCI word is detected individually frame-by-frame, more power is required to recover TFCI bits with higher reliability. Moreover, because no error checks on successful TFCIs within the TTI are performed, transport channel processing is performed regardless and power consumption is unnecessarily increased.